In a healthy person, the kidneys remove impurities from the blood and eliminate them in the urine. If the kidneys are damaged or cease to function efficiently, impurities can build up leading eventually to death. Dialysis is a medical process used to remove impurities from the body that would otherwise be removed by the kidneys. Hemo dialysis is a process wherein a patient's blood is pumped through a special filtration machine to remove impurities and then pumped back into the body. Because the required equipment is bulky and very expensive, hemo dialysis is usually performed in a dialysis clinic. The patient must visit the clinic for several hours every few days as long as the kidney condition is present. Eventually, many patients receive a kidney transplant preventing any further need for dialysis. However, there are often long waits for transplantable kidneys and consequently the patients must continue dialysis treatments for several years.
As an alternative to hemo dialysis, peritoneal dialysis was developed. The peritoneum is a abdominal membrane located below the diaphragm and separating the stomach, lungs, and heart from the intestines. Below the peritoneum is the peritoneal cavity. In peritoneal dialysis, saline solution is placed in the peritoneal cavity. Because the solution has a higher salinity than other body fluids, fluid is drawn across the peritoneum to dilute the solution. Impurities are also drawn across the peritoneum into the solution. After a period of time, the saline solution is drained from the peritoneal cavity taking the impurities with it. The solution can then be replaced with fresh saline starting the process over.
Peritoneal dialysis has multiple advantages over hemo dialysis. Many doctors and health organizations feel that it is healthier, the necessary equipment is much less expensive, and most patients can perform the process in the privacy of their own home. For peritoneal dialysis, the patient has a catheter surgically implanted into the abdomen. The catheter is used to fill and drain the peritoneal cavity. Once the catheter is installed, the only equipment necessary for peritoneal dialysis is an IV pole to hang the solution bags as the solution is fed into the peritoneal cavity, miscellaneous tubing and valves, and something to warm the solution before use. Reliable patients can be taught to perform all steps required for peritoneal dialysis in the privacy of their own home eliminating the need for frequent clinic visits. While peritoneal dialysis requires fluid changes several times a day, each change can be accomplished in a bedroom instead of a medical clinic. This gives patients increased control over their lives.
Peritoneal dialysis solution generally comes in heavy duty 2 liter bags of various strengths. The patients performs a variety of measurements to determine how well impurities are being eliminated and uses different solution strengths depending on the results. The solutions generally come in three strengths and those with higher salinity pull more impurities out of the body. Typically patients must change fluid 4 or more times a day and they may use two or three different strengths in the same day.
Peritoneal dialysis solution must be warmed to approximately body temperature before it is fed into the peritoneal cavity. Solution that is significantly cooler than body temperature will chill the body, cause cramps and be uncomfortable. Solution that is too hot will also be uncomfortable and may be hazardous. Therefore, there is a need for a device that can consistently warm a dialysis solution bag to a comfortable temperature for use in the peritoneal dialysis solution process.
The peritoneal dialysis solution should not be warmed too quickly or it can lead to nitrogen fixation, popularly known as the bends. The dialysis solution has a certain amount of air dissolved in it. When the solution is warmed, it is less able to hold the air and so the solution becomes super saturated. If the solution were allowed to remain at the warmed temperature for an extended period, some of the air would slowly work its way to the surface until the solution/air mixture reached equilibrium. However, when the solution is rapidly warmed, it is supersaturated with the air. When the freshly warmed solution is fed into the body, it passes through an IV tube and nucleation occurs creating tiny bubbles. These tiny gas bubbles are pulled into the peritoneal cavity along with the solution. These bubbles can then travel throughout the body leading to nitrogen fixation. Patients' sensitivity to this problem varies, but in some patients it creates a painful condition especially in sensitive joints. To prevent the formation of bubbles, the solution must be warmed slowly enough to allow some of the dissolved air to move out of the solution thereby establishing a new equilibrium at the warmed temperature. Therefore, there is a need for a device that can slowly and steadily warm peritoneal dialysis solution so that the formation of tiny bubbles is prevented.
While the peritoneal dialysis process is a significant improvement over hemo dialysis, it remains time consuming and greatly impacts the quality of life of a patient. A patient must test themselves several times a day, choose a proper solution bag, warm the bag slowly to a comfortable temperature being careful not to over or under heat it, drain the old solution out of the cavity, and feed the fresh solution into the cavity. There is a need to make the warming process more convenient. Warming a solution bag four or more times a day consumes a lot of time and its repetitive nature is tiring. The patient must interrupt whatever they are doing at the time for long enough to accomplish all steps of the process. It would be most convenient if solution bags could be kept warm and ready for use, especially if bags of each solution strength could be kept warm. Then, the patient could skip the warming process and proceed immediately to the drain and refill process. Therefore, there is a need for a device that will store a plurality of peritoneal dialysis solution bags at a ready for use temperature.
Since the peritoneal dialysis process is typically performed in the home, any device used for warming the solution must be suited for the home environment. This requires that the device not be overly bulky. Also, most people would rather not make their bedroom look like a doctor's office or a hospital room so a warming device for home use preferably should not look like medical equipment. The use of stainless steel, electronic readouts, and lights should be minimized. Also, a warming device for the home should not be complex, difficult to use, or require daily maintenance or cleaning. Therefore, there is a need for a peritoneal dialysis solution warming device for use in the home that blends in with the home environment, is not overly bulky, is easy to use, and does not require maintenance.
There are a variety of devices which warm solution but all fall short of meeting all of the needs of patients of peritoneal dialysis. Many attempts at fluid warming are aimed at hospital or clinic use and require the removal of the fluid from the container. This introduces a risk of introducing contamination into the fluid and makes the device using this approach unnecessarily complex and difficult to use. Many of these approaches require bulky, complex devices such as a pump to remove the fluid from the container it was stored in. Once the fluid is removed, it is generally exposed to a heating device of some type and then returned to a separate storage container. All parts of the device must be kept sterile if the fluid is to remain uncontaminated. This necessitates laborious cleaning procedures and the use of expensive, easily cleanable materials such as stainless steel. U.S. patents disclosing systems requiring the removal of solution from its container before heating include: U.S. Pat. No. 4,293,762 to Ogawa; U.S. Pat. No. 4,309,592 to Le Boeuf; U.S. Pat. No. 4,464,563 to Jewett; U.S. Pat. No. 4,678,460 to Rosner; U.S. Pat. No. 4,707,587 to Greenblatt; U.S. Pat. No. 4,844,074 to Kurucz; and U.S. Pat. No. 4,906,816 to van Leerdam.
There are also several U.S. patents directed to warming devices that do not require removal of a fluid from its container. However, each device lacks several features of the present invention. U.S. Pat. No. 4,934,336 to White is directed to an apparatus and method for the warming of intravenous equipment consisting of an insulated wrap material having a removable and reusable heat pack. This reference completely lacks the structure of the present invention and fails to provide for a temperature controller that controls the heat output of a heating device in a cabinet such that the temperature in the cabinet is regulated. The heat source in White is a heat pack that is placed in a wrap with the intravenous equipment. The temperature of the solution will vary depending on the energy in the heat pack and temperature will not be maintained for long periods. The White device is also capacity limited and intended only for portable use.
U.S. Pat. No. 4,874,033 to Chatelain et al. and U.S. Pat. No. 4,801,777 to Auerbach are directed to blood product heating methods and apparatuses. Both require the blood products to be submerged in a heated water bath. The present invention is not directed to heating blood products and does not require submersion of the fluid containers in a bath of water. The use of water makes these devices unsuitable for the home since they require access to a water source and drain. The present invention can be used in a bedroom where water is not readily available. The present invention is also significantly more convenient since the fluid filled containers do not have to be dried before use and the warming device does not have to be filled with water.
U.S. Pat. No. 4,657,004 to Coffey discloses a mobile livestock intensive care unit having a temperature controlled fluid/medicine cabinet. This cabinet lacks the specific structure of the present invention, is not suited to use in the home, is not designed to slowly warm solution, is generally vertical rather than generally horizontal, and is not aimed at peritoneal dialysis solution.
U.S. Pat. No. 5,183,994 to Bowles is directed to a heated drug box. The box relies primarily on thermal conduction and lacks the structure of the present invention. It is not designed to slowly warm solution and maintain the temperature. Rather it is directed to preventing the temperature of medicines carried outdoors in cold temperatures from dropping to a temperature that makes working with the medicines impossible or impractical. The box is not directed to peritoneal dialysis solution warming and is not large enough to store a plurality of solution bags. The reference also is not suited for use in the home.
U.S. Pat. No. 5,282,264 is directed to an apparatus for thawing and warming frozen fluids by the circulation of heated air. The reference lacks the structure of the present invention, is bulky, requires a circulation fan, and is designed for thawing frozen fluids rather than maintaining the temperature of ready to use solution.
U.S. Pat. No. 5,408,576 to Bishop is directed to an IV fluid warmer for use in an operating room. A plurality of bags are dropped through a door in the top of the generally vertical cabinet where they contact a heating element mounted on a side wall. Warmed bags are sequentially dispensed from an opening in the side of the unit near its bottom. The reference relies on thermal conduction, provides access only to the bottom-most solution bag, lacks insulation, and is designed to rapidly warm solution rather than to do so slowly. Providing access only to one solution bag at a time prevents the unit from being used to warm a variety of solution strengths. The reference is aimed at operating rooms and therefore is not well suited to home use. It also lacks the specific structure of the present invention.
While solution manufactures recommend against it, many patients warm the solution bags in the microwave. This presents two problems. The temperature of the solution bag is difficult to control. Cooking time will be highly dependent on the starting temperature of the solution bag. It is also difficult for a patient to determine the exact temperature of the bag and consequently they may inadvertently over or under cook the solution. The second problem is that bubble formation is especially prevalent with microwaving because a microwave heats unevenly. The solution will be warmed much faster where the microwave energy is concentrated than where it is not.